The present invention relates to a roller carrying mechanism which includes two sets of carrying roller units each having a drive roller and a pressing roller and a photographic processing device which incorporates the roller carrying mechanism therein.
Recently, in a digital mini laboratory (photographic processing device), an exposure method which uses an photo print head as an exposure head has been adopted. In performing the exposure using such an exposure method, the photo print head whose exposure range is extended in the main scanning direction is fixed, and a photographic paper is carried in the sub scanning direction which intersects the main scanning direction of the photo print head at a right angle by a first exposure carrying roller unit and a second exposure carrying roller unit each of which includes an exposure driving roller and an exposure pressing roller which are arranged at both sides (upstream side and downstream side in the photographic paper carrying direction) of the photo print head, whereby line exposure is sequentially performed thus completing the surface exposure of an image as a whole.
In such a roller carrying mechanism for photographic paper, the photographic paper during the exposure is transferred to the second exposure carrying roller unit from the first exposure carrying roller unit. For example, in a roller carrying mechanism as described in Japanese Laid-open Patent Publication 15768/1997, until a photographic paper reaches a first exposure carrying roller unit, a first exposure pressing roller maintains a state in which the first exposure pressing roller is brought into pressure contact with a first exposure driving roller due to a spring force to take a standby posture for receiving the photographic paper. When the photographic paper enters, the first exposure pressing roller is displaced due to the entering force of the photographic paper against the spring force and the photographic paper is directly carried to the second exposure carrying roller unit under the clamped and pressed state. In the same manner, before the photographic paper reaches the second exposure carrying roller unit, a second exposure pressing roller also maintains a state in which the second exposure pressing roller is brought into contact with a second exposure driving roller due to a spring force as a standby posture for receiving the photographic paper. Accordingly, when the photographic paper is transferred from the first exposure carrying roller unit to the second exposure carrying roller unit, the second exposure pressing roller is displaced due to the entering pressure of the photographic paper against the spring force and is directly carried in the state that the photographic paper is clamped and pressed.
In the above-mentioned roller carrying mechanism, depending on a distance between the exposure position and the second exposure carrying roller unit, there is a case in which a leading end of the photographic paper during exposure enters the second exposure carrying roller unit. In such a case, the carrying speed of the photographic paper is largely fluctuated due to an impact applied to the photographic paper at the time of clamping the photographic paper with the second exposure carrying roller unit and hence, there arises a problem that the exposure irregularity is generated on the photographic paper so that the image quality is degraded.
In view of the above-mentioned circumstances, it is an object of the present invention to provide a roller carrying mechanism which can suppress the degradation of image quality derived from the clamping of an image holding medium with a second carrying roller unit during exposure.
It is another object of the present invention to provide a photographic processing device which incorporates such a roller carrying mechanism therein.
To achieve the above-mentioned object, a roller carrying mechanism of the present invention is comprised of a first carrying roller unit which includes a first driving roller, a first pressing roller which is shiftable between a press-contact position at which the first pressing roller clamps an image holding medium between the first pressing roller and the first driving roller and is capable of performing a follower rotation and a press-contact releasing position at which the first pressing roller is released from the first driving roller, and a first pressing roller supporting shaft for supporting the first pressing roller, the first carrying roller unit being arranged at the upstream side of an image processing position, a second carrying roller unit which includes a second driving roller, a second pressing roller which is shiftable between a press-contact position at which the second pressing roller clamps the image holding medium between the second pressing roller and the second driving roller and is capable of performing a follower rotation and a press-contact releasing position at which the second pressing roller is released from the second driving roller, and a second pressing roller supporting shaft for supporting the second pressing roller, the second carrying roller unit being arranged at the downstream side of the image processing position, and a shaft coupling unit which couples the first pressing roller supporting shaft and the second pressing roller supporting shaft such that both pressing rollers are rotated in the same direction even when only one of the first pressing roller and the second pressing roller is held at the press-contact position.
According to the present invention, since the second pressing roller is shiftable between the press-contact position and the press-contact releasing position, by shifting the second pressing roller from the press-contact releasing position to the press-contact position after a leading end of an image holding medium passes between the second pressing roller and the second driving roller, an impact which is given to the image holding medium can be reduced so that the fluctuation of the carrying speed of the image holding medium can be made relatively small.
Further, since the first pressing roller supporting shaft and the second pressing roller supporting shaft are coupled to each other by means of the shaft coupling unit, by making the first pressing roller assume the press-contact position, it is possible to make the second pressing roller rotated in the carrying direction of the image holding medium. Accordingly, by making the first pressing roller assume the press-contact position at the time of shifting the second pressing roller from the press-contact releasing position to the press-contact position, it is possible to bring the image holding medium carried from the first carrying roller unit side into contact with the second pressing roller rotated in the carrying direction of the image holding medium. Eventually, an impact that the image holding medium receives from the second pressing roller can be made extremely small so that the carrying speed of the image holding medium is hardly fluctuated. Accordingly, drawbacks such as the exposure irregularity on the image holding medium and the reading irregularity on the image holding medium are hardly generated thus enhancing the image quality.
Further, since the first pressing roller is shiftable between the press-contact position and the press-contact releasing position, by shifting the first pressing roller from the press-contact position to the press-contact releasing position before a rear end of the image holding medium passes between the first pressing roller and the first driving roller, an impact applied to the image holding medium at the time of discharging the image holding medium from the first carrying roller unit can be reduced so that the fluctuation of the carrying speed of the image holding medium can be made relatively small.
In the present invention, the roller carrying mechanism may adopt the shaft coupling unit which includes a first pulley which is supported on the above-mentioned first pressing roller supporting shaft, a second pulley which is supported on the above-mentioned second pressing roller supporting shaft and a belt which is extended between the above-mentioned first pulley and the above-mentioned second pulley.
According to such a constitution, since the first and second pressing rollers are connected by means of the belt, compared to a case in which the pressing rollers are connected to each other by simply bringing these rollers into contact with each other, the rotation between these two pressing rollers can be surely transmitted.
Further, the roller carrying mechanism of the present invention may be further comprising a first one-way clutch which is disposed in a transmission system arranged between the above-mentioned belt and the above-mentioned second pressing roller and makes the above-mentioned second pressing roller perform idling with respect to the belt in the carrying direction of the above-mentioned image holding medium. Here, it is preferable that, a surface speed of the above-mentioned second pressing roller which is rotatably driven by way of the above-mentioned belt when only the above-mentioned first pressing roller assures the press-contact position is set smaller than a surface speed of the above-mentioned first pressing roller.
In the above-mentioned constitution which connects two pressing rollers using the belt, when the carrying speed is different between the first carrying roller unit and the second carrying roller unit due to the irregularity of machining accuracy of parts, an undesired force is applied to respective parts or the image holding medium due to the difference in the carrying speed between both carrying roller units and this brings about the degradation of the image quality. Accordingly, in the present constitution, the roller carrying mechanism is provided with the first one-way clutch which absorbs the difference in carrying speed between two carrying roller units derived from the irregularity of machining accuracy of parts and, at the same time, to ensure the reliable functioning of the one-way clutch, the surface speed of the second pressing roller which is rotatably driven by way of the belt when only the first pressing roller assumes the press-contact position is set smaller than the surface speed of the first pressing roller. That is, due to such a constitution, even when the carrying speed of the first carrying roller unit is greater than the carrying speed of the second carrying roller unit in the state that both of the first and second pressing rollers assume the press-contact position, the difference in the carrying speed between both units can be absorbed by the one-way clutch and hence, the undesired force is hardly applied to respective parts.
Further, when the image holding medium which is carried to the second carrying roller unit from the first carrying roller unit is brought into contact with the second pressing roller in the state that the first and second pressing rollers assume the press-contact position, the first one-way clutch functions so as to allow the second pressing roller to perform idling with respect to the belt whereby there is no fear that a large impact is applied to the image holding medium due to the contact of the image holding medium with the second pressing roller. Accordingly, drawbacks such as the exposure irregularity on the image holding medium and the image reading irregularity on the image holding medium can be hardly generated thus further enhancing the image quality.
The roller carrying mechanism of the present invention may preferably be further comprising a second one-way clutch which is disposed in a transmission system arranged between the above-mentioned belt and the above-mentioned first pressing roller and makes the above-mentioned first pressing roller perform idling with respect to the above-mentioned belt in the direction opposite to the carrying direction of the above-mentioned image holding medium.
In case that the roller carrying mechanism of the present invention adopts the constitution which uses the previously-mentioned first one-way clutch, when the state of the first and second rollers is changed from the state in which both of the first and second pressing rollers are at the press-contact position to the state in which only the second pressing roller is at the press-contact position, the angular velocity of the first pressing roller becomes faster than the angular velocity of the second pressing roller. Accordingly, when a portion of the image holding medium in the vicinity of a rear end thereof is brought into contact with the first pressing roller, there is a possibility that the image holding medium is pushed to the downstream side and hence, the carrying speed of the image holding medium is fluctuated. To the contrary, according to this constitution, even when the state of the first and second pressing rollers is changed from the state in which both of the first and second pressing rollers are at the press-contact position to the state in which only the second pressing roller is at the press-contact position, the second one-way clutch functions so that there is no possibility that the angular velocity of the first pressing roller becomes faster than the angular velocity of the second pressing roller. Accordingly, even when the portion of the image holding medium in the vicinity of the rear end thereof is brought into contact with the first pressing roller, there is no possibility that the image holding medium is pushed to the downstream side and hence, the carrying speed of the image holding medium is not fluctuated. Accordingly, drawbacks such as the exposure irregularity on the image holding medium and the image reading irregularity on the image holding medium can be hardly generated thus further enhancing the image quality.
In the roller carrying mechanism of the present invention, the diameter of the above-mentioned second pulley may be larger than the diameter of the above-mentioned first pulley. Due to such a constitution, the constitution in which the surface speed of the second pressing roller rotatably driven by way of the belt when only the first pressing roller is at the press-contact position is set smaller than the surface speed of the first pressing roller can be easily realized by adjusting the diameters of the first and second pulleys.
Further, the present invention is also applicable to a photographic processing device which incorporates any one of the above-mentioned roller carrying mechanisms. Due to such a photographic processing device, the exposure irregularity on a photographic paper as the image holding medium is hardly generated and hence, it is possible to output a print of high quality.
Other and further objects, features and advantages of the present invention will appear more fully from the following description taken in conjunction with the accompanying drawings.